Not too long ago, most consumers were satisfied that simple fitness trackers, not smartwatches, were a good way to enter the age of the “quantified self.” Sales of Fitbit’s trackers flourished, and the company held a successful IPO.

But times have changed, the numbers show. More fitness-minded people are moving to smartwatches, mainly the Apple Watch. Fitbit, which is now working on a full-fledged smartwatch of its own, may find this a dangerous era in which to live.

In the run-up to the launch of the Apple Watch back in 2014, Fitbit CEO James Park got the same question a lot: How are you going to compete? The assumption was that Apple would deliver a beautiful device that did everything a Fitbit did and much more.